HR: 0830h
AN: S51D-0075    [PDF]
TI: 3-D Shallow Shear-Wave Velocity Structure around the Source Area of the 1999 Chi-Chi (Taiwan) Earthquake by Tomographic Inversion of Short-Period Rayleigh Waves
AU: * Chang, W
EM: wychang@nsc.gov.tw
AF: National Science Council, 20F.,No.106,Sec.2,Ho-Ping E.Rd.,Taipei,Taiwan, Taipei, 106 Taiwan
AU: Hwang, R
EM: red@ftp1.gep.ncu.edu.tw
AF: Center for General Education, Van Nung Institute oftechnology, No.1, Van-Nung Rd., Chung-Li, Tao-Yuan, Taiwan, Tao-Yuan, 320 Taiwan
AU: Chen, C
EM: seichen@eq.ccu.edu.tw
AF: Institute of Seismology, National Chung-Cheng Univ., No.160,San-Shing, Ming-Hsiung, Chaiyi, 621 Taiwan
AU: Yu, G
EM: kuen@gep.ncu.edu.tw
AF: Depart. of Civil Engineering, Van Nung Institute of technology, No.1, Van-Nung Rd., Chung-Li, Tao-Yuan, Taiwan, Tao-Yuan, 320 Taiwan
AU: Chang, J
AF: Center for General Education, Hsing-Kuo College, No.89, Yu-In St.,Tainan, Tainan, 709 Taiwan
AB: By a tomographic inversion of short-period Rayleigh waves, we constructed a detailed 3-D shallow-depth shear-wave velocity structure around the source area of the 1999 Chi-Chi earthquake. Results show that the velocity systemically increased from the west to the east, and the Chelungpu fault and the Shuilikeng fault were two main boundaries to clearly divide the source area into three different geological provinces. Also, the velocity heterogeneity on the eastern side of the Chelungpu fault was stronger and more complicated than on its western side. These results could appropriately interpret the thin-skinned thrust model. For the shallow depths, the northern part of the hanging wall had a lower velocity, i.e. a lighter land, considered one of the reasons that resulted in anomalously large rupture and crustal deformation in the northern segment of the fault. In addition, results also reveal that the Chi-Chi earthquake might be initiated not only near the border on which large velocity-gradient varies but at the position where the fault plane is changed from a sharp dip-angle to a gradual one. Such this study shows that the strongly heterogeneity around the source area enables us to understand a few phenomena on seismic observations, and, then, might be likely to play an important role during the Chi-Chi earthquake rupture.
DE: 7218 Lithosphere and upper mantle
DE: 7255 Surface waves and free oscillations
SC: Seismology [S]
MN: 2003 Fall Meeting